A Nobel Prize for a Final Puzzle Piece: The Higgs Boson

The Nobel Foundation isn’t generally known for giddiness, but whoever wrote the press release announcing the winners of the 2013 physics prize evidently couldn’t resist. “HERE, AT LAST!” the headline read, followed by the declaration that François Englert, of the Free University of Brussels, in Belgium, and Peter Higgs, of the University of Edinburgh, would share the award in physics, worth about $1.25 million, for their independent prediction of a particle known as the Higgs boson—a prediction that was confirmed last year at the Large Hadron Collider, a mammoth particle accelerator that straddles the French-Swiss border, near Geneva.

“At last” is apt in this case: Higgs and Englert predicted the boson’s existence nearly fifty years ago, in order to fill a major gap in the so-called Standard Model of physics. The Standard Model is a framework that assembles and describes the fundamental particles that make up all of the matter in the universe—quarks, electrons, and neutrinos, in several varieties—plus the forces that act on them.

The problem was that the theory is only mathematically consistent if all of the particles it describes have zero mass. But if that were true, says Kyle Cranmer, a New York University physicist who played a major role in finding the Higgs in 2012, “there would be no atoms or stars or planets or life.”

Since all of these things clearly exist, there had to be some sort of missing link, and, in 1964, several teams of theorists independently suggested that the universe must be pervaded with an invisible, undetectable energy field, which came to be known as the Higgs field: as electrons and other particles moved through it, they’d encounter a sort of resistance we measure as mass. Quarks are more massive than electrons because they have more trouble moving through the Higgs field, for example.

You can’t detect the Higgs field, but if you disturb it, it responds by spitting out a particle—the Higgs. “The Higgs field is like the ocean,” says Cranmer, “and the particle is like a wave on the ocean.” Cranmer and hundreds of other experimentalists finally spotted such a wave last year, emerging from a microscopic fireball created when particles crashed into each other head-on, at nearly the speed of light.

If the Higgs hadn’t shown up at the Large Hadron Collider, the whole Standard Model would have been in trouble, and physicists would have had to go back to a half-century-old drawing board to rethink the whole thing. “The Higgs boson isn’t just the last piece of the Standard Model,” Cranmer says. “It’s the keystone that holds the whole thing together. It’s really critical.”

That being the case, it might come as a surprise that the Standard Model doesn’t explain quite as much about the universe as you might think. “The theory,” says Cranmer, “is limited in scope.” But “it’s incredibly successful at describing how stars burn and how cell phones work and pretty much everything we touch.”

Even now that it’s complete, however, the Standard Model doesn’t offer any insight into the dark matter that scientists believe pervades the cosmos, and which outweighs all visible matter by a factor of five, or dark energy, an utterly mysterious force that appears to be something like negative gravity, and is making the universe expand faster all the time. It also doesn’t reconcile quantum physics with relativity, whose fundamental incompatibility is a major unsolved problem in physics. (It’s a big reason for the development of string theory, which, essentially, postulates that the building blocks of matter aren’t particles but, rather, stringlike loops of energy. As Elizabeth Kolbert wrote in her 2007 piece about the Higgs, “In its most popular form, string theory demands the existence of seven dimensions beyond the usual four.”)

That doesn’t invalidate the Standard Model, however, any more than general relativity, Albert Einstein’s explanation of how gravity works, invalidated Isaac Newton’s law of universal gravitation. Newton’s theory works perfectly in everyday situations: when NASA calculates the trajectory of a probe to Venus or Jupiter, it uses Newton’s equations, not Einstein’s. The latter becomes necessary only when you’re in the immediate neighborhood of hugely massive objects, like the dun, or when you’re moving at speeds far higher than any space probe has ever come close to attaining.

Even if it doesn’t explain everything in the universe, the Standard Model explains plenty, and it is a big deal that it’s finally complete. The Higgs boson won’t lead to a better laser or a more powerful H-bomb or a clean energy source that will solve climate change. It’s an intellectual triumph—even a work of art, if your aesthetic runs to the underlying order of the universe.

Back in 1969, the physicist Robert Wilson testified before Congress about what might be learned from a proposed new accelerator to be built at Fermilab, outside Chicago. “Is there anything here,” asked Senator John Pastore, of Rhode Island, “that projects us in a position of being competitive with the Russians?” No, answered Wilson. “This new knowledge has all to do with honor and country but it has nothing to do directly with defending our country except to help make it worth defending.”

Michael Lemonick is a senior staff writer at Climate Central and lecturer at Princeton University; his most recent book is “Mirror Earth.”